Hello @Waldemar Werle ,
For Enterprise Dev/Test subscriptions, port 25 is blocked by default. It is possible to have this block removed. To request to have the block removed, go to the Cannot send email (SMTP-Port 25) section of the Diagnose and Solve blade in the Azure Virtual Network resource in the Azure portal and run the diagnostic. This will exempt the qualified enterprise dev/test subscriptions automatically.
After the subscription is exempted from this block and the VMs are stopped and restarted, all VMs in that subscription are exempted going forward. The exemption applies only to the subscription requested and only to VM traffic that is routed directly to the internet.
For all other subscription types:
If you are using an Enterprise Agreement subscription and still need help, contact support to get your problem resolved quickly. Use this issue type: Technical > Virtual Network > Cannot send email (SMTP/Port 25).
If none of the above helps, I would suggest you raise a support ticket with azure technical support. If you don't have the ability to open an technical support ticket, please let me know I can help you further on this.
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